Introduction
Cells are the beating hearts of living, breathing organisms especially for us humans as cells are vital to our daily functions and help us to survive even at a microscopic level. Although some cells have different shape and sizes may it be plant cells like chloroplast mesophyll in the leaves of plants or even the animal cells red blood cells in our blood, each and every one of our cells serves a major role in keeping us healthy and alive.
By definition, cells are the building blocks of life. Many organisms exist because they are made out of cells. Humans, plant even microorganisms like bacteria is considered to be alive due to the fact they are made out of cells particularly the components of the cells called organelles. These organelles define the capabilities of the cells and their functions wrapped together with a cell membrane to keep the insides of the cells from leaking out.
Membranes are one of the important factors when determining the size of the cell whether it is the thickness of the cell that makes it big or the sizes of the organelles that is wrapped by a thin membrane or even both.
In this experiment, agar cubes will be used to simulate the effect of cell sizes with a similar consistency to accurately measure the effect of cell sizes namely surface area.
Aim
To investigate the relationship between the size of the agar cube/rectangle and the rate of diffusion of sulfuric acid to decolorize the agar.
Hypothesis
The larger the surface area and the lower the volume, the rate of diffusion increases hence the volume of discoloration increases.
Materials and equipment (per group)
- 4 x small beakers (30ml)
- 0.1M sulphuric acid (25ml x 4)
- Paper Towel
- 4 x plastic spoons
- Clear plastic ruler
- Cutting tile
- Scalpel
- Stopwatch
- Disposable gloves
Procedure
- Place the jelly on the cutting tile
- Using the scalpel, cut the jelly into 4 different sized blocks (as accurately as possible) and name them A (20mm x 20mm x 20mm), B (12mm x 12mm x 12mm), C ( 20mm x 30mm x 3mm) and D (10mm x 18mm x 10mm).
- In each of the four beakers, add enough acid so that it is about 25mm deep
- Using the spoons, lower each block into its beaker of acid. Make sure that the block is completely covered by the acid. Start the stopwatch as soon as the blocks are added to the acid for 5 minutes
- After it is dried, remove the blocks from the acid using plastic spoons. Place the blocks on paper towel to dry
- After 5 minutes, use the scalpel to cut each block in half. Then using the ruler, measure the thickness of the discoloration. This is an indication of how quickly the acid diffused into the block.
- Dispose of the agar and acid using the correct methods of disposal
Results
Table 1: The percentage of block diffused with acid with different surface area and volumes
Agar Cube
Dimensions of block
The Surface area of Agar Cube (mm2)
SA
The Volume of Agar Cube (mm3)
Vi
SA : V
The Thickness of the colored section
(mm)
The Volume of the colored section
Vr
The Volume of the discoloration section Vd
% of block diffused with acid
A
20mm x 20mm x 20mm
2400
8000
0.30
12
1728
6272
78%
B
12mm x 12mm x 12mm
864
1728
0.50
4
64
1664
96%
C
20mm x 30mm x 3mm
1500
1800
0.83
1800
100%
D
10mm x 18mm x 10mm
920
1800
0.51
3
48
1752
97%
The data displayed on the table shows the surface area and volume to be the independent variable that forms a relationship with the percentage of block diffused with acid which is shown to be the dependent variable. As a result, the results collected forms a trend where when the surface area to volume ratio increases the higher the percentage of block diffused with acid.
Analysis and discussion
1. Describe any relationship between the amount of diffusion if acid in 5 minutes and the volume of the block. How do your results support this?
The relationship between the amount of diffusion of acid in 5 minutes and the volume of the block is where if the volume of the block decreases, then the amount of diffusion of acid increases in 5 minutes. The results support this relationship due to the results gathered from block A where the percentage of block diffused with acid is the lowest percentage from the rest of the agar cubes (78%) while the volume of the block is the highest (8000mm3) among the other cubes. As a result, this shows the difference and effect of volume and the amount of diffusion of acid among the cubes to form a suitable relationship.
2. Describe any relationship between the amount of diffusion of acid in 5 minutes and the surface area of the block. How do your results support this?
The higher the surface area, the greater the amount of diffusion is shown as a relationship due to the results gathered from C where C has the second highest surface area (1500mm2) but C has the second lowest volume (1800mm3) which makes the percentage of block diffused with acid the highest of all cubes.
3. Describe any relationship between the amount of diffusion of acid in 5 minutes and the SA: V of the block. How do you support this?
The relationship between the amount of diffusion of acid in 5 minutes and SA: V is where the increase in SA: V can cause the amount of diffusion of acid to increase as well. This is evident due to the evidence shown from the collection of data of cube C which has the highest SA: V value of 0.83 among all of the cubes which can be reflected to the percentage of block diffused with acid to be the highest with 100% diffusion of block. In addition, Block has the least SA: V, 0.30, among all other cubes and has the lowest percentage of block diffused with acid (78%) hence the amount of diffusion of acid in 5 minutes is effected by the SA: V.
4. Was your hypothesis supported or refuted? How do your results support this?
My hypothesis is supported by my results because the increase of surface area and volume of the cubes shows a trend with the increase of percentage of block diffused with acid. This is shown by block C where the block has the second highest surface area (1500mm2) and second lowest volume (1800mm3) hence the surface area to volume ratio is the highest (0.83) resulting in the increase of the percentage of block diffused with acid. Another block that is supporting my hypothesis is block A where although it has the highest surface area (2400mm2) and volume (8000mm3), the surface area to volume ratio is the least (0.30) which causes the percentage of block diffused with acid to be the lowest. Apart from blocks A and C, two of the blocks B and D, although their surface area and volume is the least, they have a similar surface area and volume and SA: V. This can cause their percentage of block diffused with acid to be similar (96% for B and 97% for D). Overall, the results supported my hypothesis as they show a clear trend for the surface area and volume (independent variable) affecting the percentage of block diffused with acid (dependent variable).
5. Suggest a reason why cells tend to be very small in size.
Cells tend to be very small in size due to the thickness of the membrane surrounding the cell. Most membranes of cells are thin and weak to stress and overgrowth. If they were to grow at a larger size, the organelles and cytoplasm will burst out of the cell. This experiment proves that by simulating the cell’s membrane with the use of the consistency of the agar, we can prove that the agar (simulating the membrane) can diffuse acids that can move into the cell which, in theory, can cause the cell to expand and burst.
6. Describe three safety procedures that you took during this activity. Explain why they were necessary.
One of the safety procedures which was taken during this activity is where we used cutting tiles which provides extra safety when cutting with a scalpel to prevent the table from moving and sliding which may cause the scalpel to slip and cut our fingers. Another safety procedure which was taken is by wearing lab coats that protects our bodies from dangerous chemicals like sulfuric acid which was used in the experiment. The third safety procedure is by wearing disposable gloves which protects our hands from spills and to improve the handling of glass items and chemicals.
7. Describe at least one improvement for your experiment. In what ways could you improve the quality of your data?
One improvement would be using a larger bladed knife than a scalpel which is harder to use and decreases in accuracy of data (measurements). By using a larger bladed knife it can be used to provide an increased accuracy of data when the size is needed to be measured accurately after cutting. Another improvement would be repeating the experiment for a second time which can be used to find the average thus increasing the accuracy and reliability of your data and results.
8. Outline at least one way in which you could extend this investigation. Now that you have completed this investigation, what do you want to find out next about the SA: V or cell size limitations?
Increasing the sample size can extend the investigation by providing more data which can give increased variation of data which can produce quality results during comparison and identification of trend and overall conclusion. Another way in which I can extend the investigation is by increasing the time taken from 5 minutes to 10 minutes for the blocks to be submerged in acid before being taken out. Since I have completed this investigation, I would want to find out more on the applications of SA: V and cell size limitations in more practical scenario like how it effects our bodily functions.
9. Consider the following cells. Each of the cells has the same volume. Which cell would allow for the highest rate of diffusion? Explain your answer.
Cell E would have the highest rate of diffusion because cell E has microvilli which increases the surface area thus increasing the surface area to volume ratio (SA: V). As shown by the results from the experiment, there is a trend between the SA: V and the percentage of block diffused with acid and since the cells increased in SA: V, the percentage of block diffused with acid will be higher hence causing the highest rate of diffusion.
10. Many animals curl up tightly on cold days. In hot weather, they often stretch out. Relate this behavior to the surface area to volume ratio.
Animals curl up tightly because they want to conserve heat produced by their own body. This decreases the surface area and decreases the surface area to volume ratio which also decreases the number of air molecules that is in contact with the surrounding skin and hair thus causes less evaporation and radiation of heat from the body of animals during cold days. However, during warmer or hotter days, animals would stretch out to increase the surface area of the skin and increase the surface area to volume ratio that causes more contact with the surrounding air and increases the loss of heat via evaporation of sweat and other methods of heat loss.
Conclusion
In conclusion, the results show a trend where increasing the surface area and volume or the surface area to volume ratio can increase the percentage of block diffused with acid. This is supported by the different range of data produced with each block having varying sizes. As a result, this experiment proves that the larger the block of agar (simulating cell sizes) either with an increased volume or surface area, the lower the surface area to volume ratio becomes hence this causes the percentage of block diffused to decreases. This theory works both ways with increased or decreased sizes of agar. Overall, these results support my hypothesis by supporting the theory that the increase in surface area to volume ratio also increases the percentage of block diffused with acid as well.
References
- Featherstone. D (2016) Why are cells so small? https://www.forbes.com/sites/quora/2016/08/01/why-are-cells-so-small/#6b7781dd2b35
- Weisbreger. M (2016) Why do animals hibernate?
https://www.livescience.com/54982-why-do-animals-hibernate.html
13.02.2019